Scientists Expand Knowledge of Dark Matter

nife00 writes "BBC News is reporting that British scientists at Cambridge have expanded the current understanding of the mysterious particles known as dark matter." According to the article: "[The Cambridge Team] has at last been able to place limits on how it is packed in space and measure its "temperature". "It's the first clue of what this stuff might be," said Professor Gerry Gilmore. "For the first time ever, we're actually dealing with its physics," he told the BBC News website."

Comments

How appropriate...

[Jugalator]

I just got this when first clicking on this article...

Nothing for you to see here. Please move along.

:-p

Just another point of view

[erroneus]

http://science.slashdot.org/article.pl?sid=06/01/2 5/1436243 -- This article points to the idea that there is no such thing as dark matter and explains everything with gravity. Now we're back to dark matter again? I still like science and all that but there are people who don't understand that "we don't really know everything" and that science as we know it today is merely an attempt at forming an understanding of our universe, not a definite mapping.

Re:Just another point of view

[drgonzo59]

I was actually wondering, could it be the case that we might not even be able to understand and explain some phonemena simply because our brain power is not adequate. For example the math works out for QM, but I don't think anyone can understand or conceptualize what is happening during entanglement (Einstein called it "spooky action at a distance" and never quite got to accept it).

Or when someone is talking about multi-dimensional spaces, it is easy to express it in a mathemtical form (R^6 or C^6), but what does that mean in reality, how would you think about such a space?

(Speaking of the 6 dimensions, there was an article on Slashdot about how the dark matter doesn't exist but instead we see what we do because "space has 6 dimensions".here.)

The point is that, just like dogs will never be able to solve integrals with the brain power they have now, so humans likewise might not be capable of understanding certain phenomena from the physical universe we live in.

Re:Just another point of view

[Beryllium Sphere(tm)]

That article dealt with only one kind of observation, namely how fast stars orbit the center of a galaxy.

Dark matter theory would be on pretty tenuous ground if it only explained one kind of observation.

There are features of the light from the Big Bang that are tough to explain without dark matter. The relative abundance of various nuclear isotopes is a sensitive gauge of conditions during the Big Bang, and again dark matter is the closest thing we have to an explanation.

>science as we know it today is merely an attempt at forming an understanding of our universe, not a definite mapping.

Isn't that the fun of it? My wife had a professor who always looked upward when he dropped a piece of chalk. He explained that we don't have real proof that gravity will always work, just an assumption that it will work like it always has, and if the chalk ever fell upward he sure didn't want to miss the event.

Oh, and that paper about explaining orbital motions without dark matter may have been mistaken in its methods. People who know more than we at Slashdot do have pointed out what they consider fatal flaws.

Re:Just another point of view

[meringuoid]

I was actually wondering, could it be the case that we might not even be able to understand and explain some phonemena simply because our brain power is not adequate. For example the math works out for QM, but I don't think anyone can understand or conceptualize what is happening during entanglement (Einstein called it "spooky action at a distance" and never quite got to accept it). Or when someone is talking about multi-dimensional spaces, it is easy to express it in a mathemtical form (R^6 or C^6), but what does that mean in reality, how would you think about such a space?

You needn't go off with such physical exotica as QM and multidimensional spaces. Conceptually they're weird, but they're relatively simple mathematically. Indeed, that's the great value of such mathematics: it gives us the language with which to accurately describe the unimaginable.

For a problem that seems to be truly beyond human intelligence, try turbulence. The mathematics to describe laminar fluid flows are well developed and understood, have been for centuries... but nobody has got the hang of turbulent flow. Even with supercomputer numerical simulations, you can only get so far. Proper modelling of turbulence has baffled the best minds for hundreds of years, and still we're not really any closer.

Re:Just another point of view

[Starker_Kull]

Actually, Godel did no such thing - he demonstrated that in any formal system of logic sufficiently complex to encapsulate basic arithmetic, there will be unprovable statements which are nonetheless true. Note that the reason we can say these unprovable statements are true is because that if they were false, there would exist a provable counterexample to the statement (i.e. an example of the falseness), and thus the statement would not be unprovable - but this knowledge comes from outside the logical system. In other words, he demonstrated that there will be true statements in a logical system that can never be proven within that system to be true; a hypothetical example might be Goldbach's conjecture, that any even number > 4 is the sum of two (not necessarily distinct) primes. If this was, in fact, true, but was somehow "unprovable", we would be left in the uncomfortable position of seeing billions of examples where it is true, not a single example where it was false, but of course there would always be an infinity of cases we didn't check yet. This is, in fact, the present state of our knowledge - and thus why I used it as an example. Of course, some clever egg might stumble upon a proof of Goldbach's conjecture tomorrow - people used to use Fermat's Last Theorem as a potential example of something that might be true but unprovable, until Wiles proved it. This is the problem, that we have no way of knowing what is unprovable in mathematics, because if we did have such a way of "knowing" (i.e. proving that a proposition is unprovable) for a specific proposition, we would have just proven it true, and thus it would not be unprovable! So we will never know what is not provable - we will only suspect that one of Godel's unprovable but true phantasms is staring us in the face.

My point (longwindedly) is that this has little or nothing to do with the physical, mathematically modeled, problems at hand here; if you want a better idea of the type of barrier we are facing in this case, you would be better served by complexity and information theory; look up Shannon and Chaitin for more info - that is the type of problem involved in turbulence simulation, not logical issues of provability and incompleteness.

Re:Uncertainty

[drgonzo59]

They did, but it is very dark and hard to see.

The Ministry of Silly Walks

[malia8888]

Using the biggest telescopes in the world, including the Very Large Telescope facility in Chile, the group has made detailed 3D maps of the galaxies, using the movement of their stars to "trace" the impression of the dark matter among them and weigh it very precisely.

Doesn't the name "Very Large Telescope facility" sound like it is out of a Monty Python sketch, sort of like the "Ministry of Silly Walks"?

Further, I am struck with the thought that dark matter is "Silly Putty" which has gone off a bit.

Re:The Ministry of Silly Walks

[(negative video)]

I'm personally more amused by the proposed OWL telescope, which stands for OverWhelmingly Large. It's makes you wonder what they will call the next one after that. The So Enormously Large that Gosh We're All Really Impressed Telescope?

Re:The Ministry of Silly Walks

[fruey]

"The So Enormously Large that Gosh We're All Really Impressed Telescope" sounds like it just might be accepted, were it not for the fact that the acronym SELGWARIT is a little difficult to remember, and lacks punch or reference to an animal with good eyesight (or a large animal, perhaps).

You could however, with minor adjustments, get it sounding just nice with a good acronym to boot, viz : ELEPHANT Enormously Large Exceedingly imPressive Huge Array mind-Numbing Telescope".

Ssshhhh...

[Donut2099]

"For the first time ever, we're actually dealing with its physics,"

Thats because we've secretly replaced the regular dark matter with Folger's Crystals!

No references

[Random Walk]

I'll probably never understand why newspapers are never able to quote any references for their news. Even in the absence of a published refereed paper, I would expect that there is at least a preprint or press release from the research group... apparently BBC news is convinced that their readers will drop dead on the floor if they encounter a hyperlink leading to something more than just random blurb from a journalist.

Actually, they don't even say whether 'Professor Gerry Gilmore' is part of the group that did this research, or whether he is just someone they asked 'Hey guy, what do think about this stuff?'. I.e. they don't even identify clearly any member of this 'Institute of Astronomy, Cambridge, team'.

Re:Dark Matter Blows

[meringuoid]

Dark Matter should hook up with the cosmological constant, they'd make the perfect couple.

Already done; look up 'dark energy'. Now, if you'll excuse me, I've left my dinner in the oven and I think it's burning; I smell phlogiston. Damn, with such delays I'll never get this new suit ready for the Emperor in time...

Re:What does local universe mean?

[meringuoid]

"It now looks as though the Milky Way is the biggest galaxy in the local Universe, bigger even than Andromeda. It was thought until just a few months ago that it was the other way around."

Could someone explain what the "local universe" is? And how does this compare to the entire universe?

Our local cluster of galaxies - which IIRC consists of three giant spirals and a whole bunch of small cloudlike galaxies - is unimaginatively titled the Local Group.

Hitherto it's been thought that the Andromeda galaxy was the largest in this group, with our own Galaxy about two thirds its size. Now, it seems that's not the case... damn, my childhood astronomy books lie to me again! :)

Obligatory

[SeaFox]

So I guess you could say they're shedding some light on dark matter?

Re:What does local universe mean?

[joe user jr]

Probably they mean the Local Group: "the group of galaxies that includes our galaxy, the Milky Way. The group comprises over 30 galaxies, with its gravitational center located somewhere between the Milky Way and the Andromeda Galaxy. The galaxies of the Local Group cover a 10 million light year diameter (see 1 E23 m for distance comparisons). The group belongs to the Virgo Supercluster."

In other news...

[jettoki]

British scientists at Cambridge have also placed limitations on the possible properties of the luminiferous aether. "We're pretty sure it's not yellow," says one researcher, "and we've also ruled out blue and pink. It's nice to know that we'll soon have figured out both this dark matter stuff and the luminiferous aether. Then we can start puzzling out those epicycles again."

Re:weird internal modes?

[Stalyn]

What the findings suggest is that dark matter isn't exotic matter but a different kind of matter all together. The hierarchy of forces according to interaction goes gravity -> electroweak -> strong. This means all matter we know of interacts with gravity, all matter (until recently) interacts with the electroweak force and a subset of matter, quarks, interacts with the strong force. Note, quarks also interact with the electroweak force since protons and neutrons have electric charge and these particles are made of quarks. However leptons, like the electron do not interact with the strong force.

Now it was possible that dark matter could interact with the electroweak force but very weakly and therefore undetectable at large scales. It was assumed that this meant they were very cold and at very low energy states. However if they are moving at 9km/s that would mean they have high energy states. Therefore if they did interact with the electroweak force, they would be absorbing or emitting photons. But they aren't.

So we have a new type of matter with that only interacts with standard matter(leptons, quarks) via the gravitational force.

Here's what makes me unhappy

[rknop]

Here's what makes me unhappy:

The Cambridge University team expects to submit the first of its results to a leading astrophysics journal in the next few weeks.

I don't like this "press release before publication" mode of doing science. It's all about making sure that you get the attention and public recognition, and not about propery distributing the results so that others can understand and evaluate what you've done. Alas, it seems that Marketing Is All in the modern world, and not just in the USA any more. You can be sure that the institutions who house these scientists love to get the attention and so forth.

I'd be happier if the paper had already been accepted by some real journal, with a preprint available on www.arxiv.org. As it is... we have a press release and a pop-sci article about an intersting result that's hard to truly evaluate. The article is mostly good and sounds reliable, but in my experience these pop-sci articles usually get something wrong. (For instance, even though 10,000 degrees sounds "hot", given the likely mass of the Dark Matter particle, it still is "cold" in the cosmological sense of "cold dark matter", which really means "nonrelativistic dark matter". I'm not sure how much of a surprise that temperature is, but it's probably not enough to make CDM wrong.)

-Rob